A North Hills man pleaded guilty Tuesday to a federal conspiracy charge for helping operators of sham “pop-up” medical clinics divert millions of prescription pills — including oxycodone and other addictive narcotics — to the black market.

Ralph Manning, 53, is expected to be sentenced June 11 in Los Angeles federal court.

Manning admitted working as a principal drug courier. His alleged boss, Minas “Maserati Mike” Matosyan of Encino, is charged with leading the scheme and controlling six of the sham clinics.

The U.S. Attorney’s Office alleges that Matosyan, who faces trial in August, hired corrupt doctors who allowed the conspirators to issue fraudulent prescriptions under their names in exchange for kickbacks.

Manning delivered fraudulent prescriptions and “bulk quantities” of narcotic pills as part of the scheme, according to his plea agreement.

Members of the conspiracy profited from illicit prescriptions that were issued without any legitimate medical purpose through a series of clinics that periodically opened and closed in a “nomadic” style, according to the indictment returned last summer against Matosyan, Manning and 10 others — including Glendale-based criminal defense attorney Fred Minassian.

The phony prescriptions allowed the conspirators to obtain bulk quantities of prescription drugs that were sold on the street, according to the indictment, which charged the dozen defendants with such crimes as conspiracy and obstruction of justice for allegedly creating fraudulent medical records in an effort to deter the investigation.